A contrast shower is the cheapest version of hot-cold therapy: finish a normal hot shower with a burst of cold. It needs no tub and no chiller.
This article covers the largest trial of the habit. It sits under our overview of contrast therapy benefits. It is general information, not medical advice.
Short answer: a 2016 randomized trial of 3,018 adults in the Netherlands found that ending a daily hot shower with 30, 60, or 90 seconds of cold cut self-reported sick days from work by 29%. It did not reduce the number of days people were ill. Most participants kept it up, and the most common side effect was a lingering cold feeling.
What the trial did
Buijze (2016) found the result most cold-shower claims point to. The trial in PLOS One, called the “Cool Challenge,” randomized 3,018 adults aged 18 to 65 without severe illness into four groups. Three groups ended a hot shower with 30, 60, or 90 seconds of cold every day for 30 days; a control group showered as usual. The cold water averaged about 10 to 12°C, roughly 50 to 54°F.
What it found
| Outcome | Hot-to-cold showers vs control |
|---|---|
| Self-reported sickness absence from work | 29% lower (incidence rate ratio 0.71) |
| Days of illness | No significant difference |
| Quality of life (mental score) | Slightly higher at 30 days; no difference at 90 days |
| Most reported benefit | More perceived energy |
| Completed the 30 days | 79% |
| Kept going afterward | 64% |
The authors summed it up:
The routine “resulted in a statistical reduction of self-reported sickness absence but not illness days.”
Buijze GA, et al., PLOS One, 2016
Why sick days fell but illness didn’t
People in the cold-shower groups were ill as often, but reported missing less work. The trial wasn’t blinded, so participants knew their group. Although the 29% figure is striking, it’s self-reported, and the authors didn’t find fewer days of illness.
Side effects
There were 20 serious adverse events, all judged unrelated to the showers. The most common mild effect was a lasting cold sensation, reported in the body by 196 participants and in the hands or feet by 257.
Limitations
The trial covered healthy working adults in a Dutch winter, January to March 2015. It measured sick days, not recovery from exercise, so it says nothing about sore muscles. Cleveland Clinic’s cold plunge guidance lists heart disease, high blood pressure, diabetes, pregnancy, and circulation conditions as reasons to talk to a doctor before cold exposure.
Here’s what the ad won’t tell you. Shower water in the trial was about 10 to 12°C. Tap water elsewhere, or in summer, may be much warmer.
My rule of thumb: try the 30-second version for a month before you spend money on a plunge. Most people in the trial stuck with it, and it costs nothing.
Bottom line: ending a hot shower with cold reduced reported sick days in one large trial, but not actual illness. It’s a free way to try cold exposure. For the wider evidence on hot-cold routines, see the contrast therapy benefits overview linked above.
Sources
- Buijze GA, et al., “The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial,” PLOS One, 2016: journals.plos.org
- Cleveland Clinic, “Are ‘Cold Plunge’ Ice Baths Good for You?” May 8, 2026: health.clevelandclinic.org